COMPOUND FOR SPECIFICALLY BINDING TO AMYLOID ß-PROTEIN

ABSTRACT

Provided is a compound for specifically binding to amyloid β-protein. The compound has thereon a nuclide with a large thermal neutron capture cross section and the compound is capable of specifically binding to the amyloid β-protein. The property of the compound allows it to be used in conjunction with a neutron capture therapy device to eliminate amyloid β-protein. Similarly, when the compound is labelled with radioactive element  11 C, the compound can also be used in conjunction with PET/CT for determining the part of the brain where amyloid β-protein is deposited, for diagnosing Alzheimer&#39;s disease. Also disclosed is a preparation process for the compound. The beneficial effect of the present disclosure is to make the therapy and diagnosis of Alzheimer&#39;s disease more targeted by providing the compound for specifically binding to amyloid β-protein.

RELATED APPLICATION INFORMATION

This application is a continuation of International Application No.PCT/CN2016/111815, filed on Dec. 23, 2016, which claims priority toChinese Patent Application No. 201511022559.5, filed on Dec. 30, 2015,the disclosures of which are hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to the field of medical technology, andin particularly to a compound for specifically binding to amyloidβ-protein, preparation process and use thereof for the preparation of amedicament.

BACKGROUND OF THE DISCLOSURE

The current research shows that the deposition of amyloid β-protein isclosely related to the pathogenesis of Alzheimer's disease (AD).Therefore, the detection of amyloid β-protein and how to eliminate orreduce amyloid β-protein have become the focus of research. To furtherinvestigate or elimination amyloid β-protein, there is a need for acompound that specifically binds to amyloid β-protein.

With the development of neutron capture therapy technology, the use ofneutron capture therapy to eliminate amyloid β-protein has highertargeting and better therapeutic effect, however, no compound has beenfound that can combine with the neutron capture therapy with the capableof specifically binding to amyloid β-protein.

SUMMARY

In order to solve the above technical problems, an aspect of the presentdisclosure provides a compound for specifically binding to amyloidβ-protein, and the compound has a structure as shown in formula I:

wherein R₁ is —B(OH)₂, R₂ is —NHCH₃; and the boron element in R₁ is anuclide ¹⁰B with a large thermal neutron capture cross section.

The nuclide with a large thermal neutron capture cross section include,but are not limited to, ¹⁰B, ¹⁵⁵Gd or ¹⁵⁷Gd. Wherein the nuclide with alarge thermal neutron capture cross section refers to a nuclide having aneutron capture cross section greater than or equal to 100 times of theneutron capture cross section of the basic constituent elements (C, H,O, N, P, S) of the human body under the same energy of thermal neutronirradiation. Wherein H has the largest neutron capture cross sectionamong the basic constituent elements of the human body under the sameenergy of thermal neutron irradiation. Under the condition of thermalneutron energy of 0.025 eV, the thermal neutron capture cross section ofH is 0.2 barn, the thermal neutron capture cross section of ¹⁰B is 3800barn, the thermal neutron capture cross section of ¹⁵⁵Gd is 60700 barn,and the thermal neutron capture cross section of ¹⁵⁷Gd is 254000 barn,all are greater than 100 times of the thermal neutron capture crosssection of the H element under the same energy of thermal neutronirradiation.

This kind of nuclides with a large thermal neutron capture cross sectionmay react with the thermal neutrons to release at least one lethalradiation that has a short range and substantially destroys thestructure of the amyloid β-protein that specifically binds to thecompound, without destroying other normal tissue, thus the damage tonormal tissue is very little.

The nuclide ¹⁰B undergoes the following reaction under the irradiationof the neutron beam:

Two heavy particles of ⁴He and ⁷Li are generated by ¹⁰B(n,α) ⁷Li neutroncapture and nuclear splitting reaction utilizing the characteristics ofboron-containing (¹⁰B) compound that with a large thermal neutroncapture cross section. As shown in Reaction Formula I, the averageenergy of the two heavy particles is about 2.33 MeV, withcharacteristics of high linearity transfer (LET), and short range. Thelinear energy transfer and range of α particles is 150 keV/nm, 8 nm,respectively, while that of ⁷Li heavy particles is 175 keV/μm, 5 μm. Thetotal range of the two particles is equivalent to about the size of onecell, so the radiation damage to the organism is limited to the celllevel.

The compound has a property of specifically binding to the amyloidβ-protein and has a nuclide ¹⁰B with a large thermal neutron capturecross section. Therefore, after forming a conjugate with the amyloidβ-protein, the conjugate is irradiated with a neutron beam generated bya neutron capture therapy device.

It is preferred that in the compound for specifically binding to theamyloid β-protein, the carbon element in R₂ of the compound is ¹¹C.

The element ¹¹C as a radionuclide is often used to label compounds formedical diagnosis and use. The compound2-(4-methylaminophenyl)-6-dihydroxyboroobenzothiazole provided by thepresent disclosure has a property of specifically binding to the amyloidβ-protein, and after labeling the compound with the radionuclide ¹¹C,the compound can be used in PET/CT to track and determine the parts ofamyloid β-protein deposition in the brain for AD diagnosis.

According to another aspect of the present disclosure, there is provideda process for preparing the compound for specifically binding to theamyloid β-protein, wherein the compound of formula I is prepared fromthe compound 6-bromo-2-(4-nitrophenyl)benzothiazole of formula II:

The compound capable of specifically binding to the amyloid β-protein ofthe formula I is 6-borono-2-(4-methyl aminophenyl)benzothiazole.

It is preferable that in the preparation process of the compound forspecifically binding to the amyloid β-protein, the process for preparing6-borono-2-(4-methyl aminophenyl)benzothiazole from6-bromo-2-(4-nitrophenyl)benzothiazole including steps of:

reducing 6-bromo-2-(4-nitrophenyl)benzothiazole to obtain6-bromo-2-(4-aminophenyl)benzothiazole;

reacting 6-bromo-2-(4-aminophenyl)benzothiazole and formaldehyde toobtain 6-bromo-2-(4-methyl aminophenyl)benzothiazole;

reacting 6-bromo-2-(4-methyl aminophenyl)benzothiazole andbis(pinacolato)diboron to obtain 2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole;wherein the boron in bis(pinacolato)diboron is ¹⁰B;

oxidizing 2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazoleby an oxidizing agent to obtain the compound 6-borono-2-(4-methylaminophenyl)benzothiazole of formula I.

It is preferred that 6-borono-2-(4-methylaminophenyl)benzothiazole canalso be prepared from 6-bromo-2-(4-nitrophenyl)benzothiazole includingsteps of:

reacting 6-bromo-2-(4-nitrophenyl)benzothiazole withbis(pinacolato)diboron to obtain2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole;wherein the boron in bis(pinacolato)diboron is ¹⁰B;

oxidizing2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazoleby an oxidizing agent to obtain 6-borono-2-(4-nitrophenyl)benzothiazole;

reducing 6-borono-2-(4-nitrophenyl)benzothiazole by a reducing agent toobtain 6-borono-2-(4-aminophenyl)benzothiazole;

reacting 6-borono-2-(4-aminophenyl)benzothiazole, methyl iodide andsilver trifluoromethanesulfonate to obtain the compound6-borono-2-(methylaminophenyl)benzothiazole of formula I.

In the above-mentioned two steps of synthesizing6-borono-2-(4-methylaminophenyl)benzothiazole, the element ¹⁰B of thecompound of formula I is derived from the element ¹⁰B of the reactantbis(pinacolato)diboron used. As described above, in preparing thecompound of the formula I, the content of the ¹⁰B-containingbis(pinacolato)diboron in the reactant bis(pinacolato)diboron should beselected according to the purity of the ¹⁰B-containing compound requiredfor practical application.

In addition, the element C in methyl iodide can be ¹²C or ¹¹C. It isfurther preferred that in the preparation process of the compound forspecifically binding to the amyloid β-protein, the carbon in the methyliodide is ¹¹C. The 6-borono-2-(4-methylaminophenyl)benzothiazolesynthesized from radioactive labeled methyl iodide is also radioactiveand the radioactive ¹¹C is labeled on the methylamine group of R₂ of thecompound of formula I.

The compound of formula I can be labeled with ¹¹C and used to track thepart of amyloid β-protein deposition in the brain by using itsradioactivity in combination with Positron Emission Computed Tomography(PET) for AD diagnosis. It should be noted that even if the compound offormula I is labeled with ¹¹C, the compound still has a property ofspecifically binding to the amyloid β-protein, and the compound stillcontains a nuclide ¹⁰B with large thermal neutron capture cross section.Therefore, the compound of formula I, which is labeled with ¹¹C, stillhas a function for eliminating amyloid β-protein in the neutron capturetherapy system.

It is preferred that in the preparation process of the compound forspecifically binding to the amyloid β-protein, the oxidizing agent maypreferably be sodium metaperiodate or other oxidizing agent having asimilar oxidizing ability to sodium metaperiodate;

The third aspect of the present disclosure provides the use of6-borono-2-(4-methylaminophenyl)benzothiazole in the preparation of amedicament for specifically binding to amyloid β-protein. The medicamentprepared from 6-borono-2-(4-methyl aminophenyl)benzothiazole forms aconjugate with amyloid β-protein, and the conjugate is irradiated withneutron rays radiated by a neutron capture therapy device. The neutronsand ¹⁰B elements react to produce energy that destroys amyloidβ-protein.

The fourth aspect of the present disclosure provides the use of¹¹C-labeled 6-borono-2-(4-methylaminophenyl)benzothiazole in thepreparation of a PET imaging agent for amyloid β-protein.

The beneficial effects of the present disclosure are, on the one hand,by providing a novel compound capable of specifically binding to amyloidβ-protein, to achieve the elimination of amyloid β-protein thatspecifically binds to the compound by means of a neutron capture therapydevice, providing a new way of idea and process to eliminate amyloidβ-protein; on the other hand, by providing a 6-borono-2-(4-methylaminophenyl)benzothiazole labeled with radioisotope ¹¹C, to provide anew choice for the PET imaging agent for amyloid β-protein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H NMR spectrum of6-borono-2-(4-methylaminophenyl)benzothiazole;

FIG. 2 is a schematic plan view of a neutron capture therapy device foran accelerator neutron source;

FIG. 3 is a schematic plan view of a neutron capture therapy device fora reactor neutron source;

Graphs (1) and (2) in FIG. 4 are the stability spectrum of ¹¹C-labeled6-borono-2-(4-methylaminophenyl)benzothiazole at 30 min and 60 min,respectively;

Graphs A and B in FIG. 5 are PET images of the control and SAMP8 modelmice at 30 minutes after the injection of labelled 2-(4-methylaminophenyl)-6-dihydroxyboroobenzothiazole, respectively.

FIG. 6 is an SDS-PAGE electrophoresis pattern of the mixed solution ofbovine serum albumin and H₃ ¹⁰BO₃ irradiated with radiation at differentpositions from the exit of the collimator, respectively.

DETAILED DESCRIPTION

The present disclosure will now be described in further detail withreference to the accompanying drawings in order to enable those skilledin the art to implement with reference to the teachings.

It is to be understood that the terms “having”, “comprising”,“including” as used herein do not exclude the presence or addition ofone or more other ingredients or combinations thereof.

The fast neutrons herein neutrons with energy range of greater than 40keV, epithermal neutron with energy range of 0.5 eV to 40 keV, andthermal neutron with energy range of less than 0.5 keV.

The compound for specifically binding to amyloid β-protein provided bythe present disclosure is 6-borono-2-(4-methylaminophenyl)benzothiazole,and the structure thereof is confirmed as shown in FIG. 1. The compoundscan be combined with a neutron capture therapy device to eliminateamyloid β-protein deposition plaques.

As shown in FIG. 2 or FIG. 3, the neutron capture therapy deviceincludes a neutron source, a beam shaping assembly and a collimator,wherein the beam shaping assembly includes a reflector, a moderator, athermal neutron absorber and a radiation shielding means, wherein theneutron source includes an accelerator-based neutron source and areactor-based neutron source.

In the practical application of the neutron capture therapy system toeliminate amyloid β-protein, it is usually necessary to adjust the fastneutrons in the mixed radiation field to the superheat neutrons andreduce the amount of other harmful rays in the mixed radiation field inthe beam shaping of the neutron capture therapy device. In the practicalapplication of the neutron capture therapy system to eliminate amyloidβ-protein, it is usually necessary to adjust the fast neutrons in themixed radiation field to the epithermal neutrons and reduce the amountof other harmful rays in the mixed radiation field in the beam shapingassembly of the neutron capture therapy device. However, consideringthat in the process of neutron beam travelling from the collimator ofthe neutron capture therapy device to a compound that specifically bindsto the amyloid β-protein, the energy of the neutron beam will have acertain degree of attenuation as the distance between the two increases,and in the process for the neutron beam to arrive at the compound thatspecifically binds to the amyloid β-protein, there are often othersubstances moderating the energy of the neutrons in varying degrees,thus, in order to ensure the energy and neutron intensity of theneutrons arriving at the compound that specifically binds to the amyloidβ-protein, it is usually necessary to slow the fast neutrons in the beamshaping assembly to epithermal neutrons and to increase the amount ofepithermal neutrons in the neutron beam coming out of the collimator.

Referring again to FIG. 2, the neutron capture therapy device in theneutron capture therapy system is a neutron capture therapy device forthe accelerator neutron source, wherein the accelerator 10 a acceleratesthe proton, expands the cross-sectional area of the proton beam P by thebeam expander 20, causes the proton beam P to hit the target T andgenerate neutrons. The reaction principle is that the charged particlessuch as proton and deuteron are accelerated by the accelerator to energyenough to overcome the target nucleus Coulomb repulsion, and carry out anuclear reaction with the metal target T producing nuclei and neutrons,wherein, the commonly used metal targets are usually lithium andberyllium. By this method, a mixed radiation field is generated, whenacting on amyloid β-protein 53 using the neutron capture therapy device,it is necessary to reduce the other kinds of rays as much as possible.And the moderator 32 a in the beam shaping assembly 30 a has the effectof adjusting the energy of the mixed radiation field, and the reflector31 a reflects the mixed radiation field diffused in the other directionto reduce the loss of the neutron. The beam shaping assembly 30 a mayalso include a thermal neutron absorber 33 a capable of absorbing lowerenergy of the thermal neutrons. The beam shaping assembly 30 a isprovided with a radiation shielding means 34 a outside to prevent theradiation from causing damage to the nearby person. The collimator 40 ais mounted at the rear of the beam shaping assembly 30 a, and the beamafter adjustment by the beam shaping assembly 30 a is then converged bythe collimator 40 a to more accurately irradiate the compound 52containing the nuclide 51 with a large thermal neutron capture crosssection and capable of specifically binding to the amyloid β-protein 53.The epithermal neutron beam is more fully utilized.

Referring again to FIG. 3, the neutron capture therapy device in theneutron capture therapy system is a neutron capture therapy device forthe reactor neutron source, wherein the reactor neutron source 10 bpasses the generated neutron beam N to the beam shaping assembly 30 bthrough a pipe. Both the reactor neutron source 10 b and the neutronsource of the accelerator 10 a generate a mixed radiation field. Thefast neutrons having a high energy in the mixed radiation field areslowed by the moderator 32 b in the beam shaping assembly 30 b toneutrons that can destroy the structure of amyloid β-protein. The raysdiffused in the other directions are reflected back into the moderator32 b through the reflector 31 b to improve the utilization of theradiation. The thermal neutron absorber 33 b in the beam shapingassembly can absorb the lower thermal neutrons in the mixed radiationfield so that the epithermal neutron content in the neutron beam N ishigher. The neutron beam N, after the convergence of the collimator 40b, can be used to more accurately irradiate the compound 52 containingthe nuclide 51 with a large thermal neutron capture cross section andcapable of specifically binding to the pathogenic protein 53. Theepithermal neutron beam is more fully utilized.

The technical solutions of the present disclosure will be furtherdescribed with reference to the following examples.

The compounds that specifically binds to amyloid β-protein described inthe preferred embodiments of the present disclosure refer to6-borono-2-(4-methylaminophenyl)benzothiazole, wherein the boron elementon the compound is ¹⁰B and the compound may contain a radioactiveelement ¹¹C. The boron elements in the boron-containing compoundsdescribed in the preferred embodiments of the present disclosure contain¹⁰B, unless otherwise specified.

Example 1 Preparation of a Compound that Specifically Binds to Amyloidβ-Protein

The compound 6-borono-2-(4-methylaminophenyl)benzothiazole of theformula I can be prepared by steps of:

1 g of 6-bromo-2-(4-nitrophenyl)benzothiazole was dissolved in 10 mL ofethanol and 5.39 g of SnCl₂.2H₂O was added. The reaction was stirred at100° C. for 1 h to obtain 6-bromo-2-(4-aminophenyl)benzothiazole;

¹H NMR: 400 MHz DMSO

δ 8.29 (s, 1H), 7.80-7.82 (d, J=8.8 Hz, 1H), 7.74-7.76 (d, J=8.8 Hz,2H), 7.58-7.60 (m, 1H), 6.65-6.67 (d, J=8.4 Hz, 2H), 5.95 (s, 2H).

To 1 g of 6-bromo-2-(4-aminophenyl)benzothiazole was added 16.4 mmol offormaldehyde, 10 mL of tetrahydrofuran (THF) and 20 mL of methanol wereadded thereto, and 0.886 g of sodium methoxide was added in one portion,and the reaction solution was stirred at 65° C. for 12 h, and then wascooled to 25° C., 620.41 mg of sodium borohydride (NaBH₄) was added andthe reaction temperature was raised to 65° C. The reaction was stirredfor 1 h to obtain 6-bromo-2-(4-methylaminophenyl)benzothiazole;

¹H NMR: 400 MHz CDCl₃

δ 7.97 (s, 1H), 7.89-7.91 (d, J=8.8 Hz, 2H), 7.81-7.83 (d, J=8.8 Hz,1H), 7.52-7.54 (m, 1H), 6.64-6.66 (d, J=8.8 Hz, 2H), 2.93 (s, 3H).

A reaction system consisted of 100 mg of6-bromo-2-(4-methylaminophenyl)benzothiazole, 95.46 mg ofbis(pinacolato)diboron and 92.23 mg of potassium acetate. To thereaction system was added 4 mL of THF and 2 mL of dimethylsulfoxide(DMSO). 26.39 mg of dichlorobis (triphenylphosphine) palladium(Pd(PPh₃)₂Cl₂) was added under nitrogen at 20° C. and the reaction wasstirred at 90° C. for 12 h to obtain 2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole, wherein the boron in the bis(pinacolato)diboron includes ¹⁰B;

¹H NMR: 400 MHz MeOH

δ 8.26 (s, 1H), 7.82-7.86 (m, 4H), 7.76-7.93 (m, 2H), 4.07 (s, 1H), 2.63(s, 3H), 1.2 (s, 12H).

300 mg of 2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole was added to 20 mL of THF and 10 mL of water, and then875.93 mg of sodium metaperiodate (NaIO₄) was added to form a reactionsystem. The reaction system was stirred at 25° C. for 12 h to obtain thecompound of formula I: 6-borono-2-(4-methylaminophenyl)benzothiazole.The ¹H NMR scan spectrum of the compound is shown in FIG. 1.

¹H NMR: 400 MHz MeOH

δ 8.27 (s, 1H), 7.83-7.85 (m, 4H), 6.66-6.68 (d, J=7.6 Hz, 2H), 2.85 (s,3H).

Wherein, 6-bromo-2-(4-nitrophenyl)benzothiazole can be prepared by stepsof:

5 g of 6-bromo-2-amino-benzothiazole was added to 25 mL of a solution ofpotassium hydroxide at a concentration of 10 M, and then 5 mL ofethylene glycol was added to form a mixed solution which was stirred at125° C. for 2 h to obtain 2-amino-bromophenyl mercaptan;

¹H NMR: 400 MHz DMSO

δ 7.21-7.26 (m, 1H), 6.99 (s, 1H), 6.81-6.72 (m, 1H), 6.39 (s, 1H), 5.72(s, 2H).

1.48 g of p-nitrobenzaldehyde was added to 2 g of 2-amino-5-bromophenylmercaptan, and then 40 mL of DMSO was added to form a reaction solution,which was stirred at 180° C. for 0.5 h to obtain6-bromo-2-(4-nitrophenyl)benzothiazole;

¹H NMR: 400 MHz DMSO

δ 8.54 (s, 1H), 8.34-8.41 (m, 4H), 8.07-8.09 (d, J=8.8 Hz, 1H),7.74-7.77 (m, 1H).

The specific reaction procedure for the synthesis of6-borono-2-(4-methylaminophenyl)benzothiazole in this example is shownin Scheme II (The boron element in the scheme includes ¹⁰B):

Example 2 Preparation of a Compound that Specifically Binds to Amyloidβ-Protein

The synthesis method of 6-bromo-2-(4-nitrophenyl)benzothiazole in thisexample is the same as that shown in Example 1.

To 100 mg of 6-bromo-2-(4-nitrophenyl)benzothiazole was added 90.91 mgof bis(pinacolato)diboron and 87.84 mg of potassium acetate, then, 4 mLof THF and 2 mL of DMSO was added, and 25 mg of dichlorobis(triphenylphosphine) palladium was added under nitrogen at 20° C., andthe reaction system was stirred at 95° C. for 15 h to obtain2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole,wherein the boron in the bis(pinacolato)diboron includes ¹⁰B.

¹H NMR: 400 MHz CDCl₃

δ 8.44 (s, 1H), 8.35-8.37 (d, J=8.8 Hz, 2H), 8.28-8.30 (d, J=8.8 Hz,2H), 8.11-8.13 (d, J=8 Hz, 1H), 7.96-7.98 (d, J=8 Hz, 1H), 1.40 (s,12H).

To 539.7 mg of2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazolewas added 30 mL of THF and 10 mL of water, followed by the addition of1.51 g of sodium metaperiodate, the reaction system was reacted at 25°C. for 23 h to obtain 6-borono-2-(4-nitrophenyl)benzothiazole;

¹H NMR: 400 MHz DMSO

δ 8.56 (s, 1H), 8.36-8.42 (m, 4H), 8.29 (m, 2H), 8.10-8.12 (d, J=8.4 Hz,1H), 8.00 (m, 1H).

To 100 mL of methanol was added 200 mg of catalyst Pd/C, and then 180 mgof 6-borono-2-(4-nitrophenyl)benzothiazole was added to form a reactionsystem, the reaction system was vacuum degassed in a hydrogen atmosphereand reacted at 25° C. for 10 min to obtain6-borono-2-(4-aminophenyl)benzothiazole;

¹H NMR: 400 MHz MeOH

δ 8.29 (s, 1H), 7.80-7.84 (m, 4H), 6.74-6.76 (d, J=8.8 Hz, 2H).

Methyl iodide was carried by nitrogen to pass through a silvertrifluoromethanesulfonate tube heated to 200° C., and then passed intoanhydrous acetone in which 6-borono-2-(4-aminophenyl)benzothiazole wasdissolved to form a reaction solution, the reaction solution was reactedat 80° C. for 5 min and quenched with water to obtain6-borono-2-(4-methylaminophenyl)benzothiazole.

Wherein the element C in the methyl iodide may be a radioactive ¹¹C,thus, 6-borono-2-(4-methylaminophenyl)benzothiazole synthesized from italso has a radioactive element ¹¹C, therefore, the radioactive compoundcan be used in conjunction with PET to track the site of amyloidβ-protein deposition in the brain and the diagnosis of AD.

¹H NMR: 400 MHz MeOH

δ 8.27 (s, 1H), 7.83-7.85 (m, 4H), 6.66-6.68 (d, J=7.6 Hz, 2H), 2.85 (s,3H).

The reaction procedure of this example is shown in Scheme III (The boronelement in the scheme includes ¹⁰B):

Example 3 Use of 6-Borono-2-(4-Methylaminophenyl)Benzothiazole in thePreparation of a PET Imaging Agent for Amyloid β-Protein

By an experimental method well known to those skilled in the art, the6-borono-2-(4-methylaminophenyl)benzothiazole labeled with synthesizedin Example 2 was purified by preparative HPLC to give a radioactivechemical purity of 98.15%, with a retention time of 5.43 min, which wasconsistent with the retention time of the standard sample of6-borono-2-(4-methylaminophenyl)benzothiazole, thus the purified productwas confirmed to be the desired radioactive compound.

The stability of ¹¹C-labeled6-borono-2-(4-methylaminophenyl)benzothiazole in vitro was determined byHPLC, at selected time of 30 min and 60 min. In FIG. 4, graph (1) showsthe radioactivity spectrum of stability for 30 min, (2) theradioactivity spectrum of stability for 60 min, and radioactive chemicalpurity at 30 min and 60 min were both 100%. Therefore, the radioactivechemical purity of the ¹¹C-labeled radioactive compound met theexperimental requirements.

Example 4 Experiment of ¹¹C-Labeled6-Borono-2-(4-Methylaminophenyl)Benzothiazole Specifically Binding toAmyloid β-Protein

SAMP8 (senescence accelerated mouse prone 8) mice are the most commonanimal model of AD (Alzheimer's disease), in its brain there are a largenumber of amyloid deposition plaque. In this example, SAMP8 mice wereused as model mice, and the normal mice were used as the control mice.Both the model mice and the control mice were 10 months old. The twomice were injected with 6-borono-2-(4-methylaminophenyl)benzothiazolecontaining ¹¹C labeling, and the Micro-PET scan is used to study whether6-borono-2-(4-methylaminophenyl)benzothiazole and amyloid β-protein havespecific binding properties. Model mice and control mice weighing31.5±0.3 g were selected, 31.0±0.6 μCi of ¹¹C labelled6-borono-2-(4-methyl aminophenyl)benzothiazole were injected thereto,and Micro-PET of Model INVEON from Siemens were used for scan, where thescanning window was 350-650 KeV.

It is well known to those skilled in the art that the major cause ofAlzheimer's disease is that the amyloid β-protein deposition plaquesaccumulate in the cerebral cortex and hippocampus of the brain. In thisexample, Micro-PET scanned and compared the brains of the model andcontrol mice using PMOD software. And the absorption of radioactive6-borono-2-(4-methylaminophenyl)benzothiazole in the cerebral cortex andhippocampus of SAMP8 model mice and control mice was determined, tofurther illustrate that the compound is capable of specifically bindingto amyloid β-protein deposition plaques. The specific results are shownin Table 1 and Table 2:

TABLE 1 The uptake of radioactive6-borono-2-(4-methylaminophenyl)benzothiazole in cerebral cortex ofmodel mice and control mice Cerebral cortex uptake ofradiopharmaceuticals (% ID/g) Time after Ratio (modelradiopharmaceutical Model Control mice/control injection (min) mice micemice) 5 3.03 1.61 1.9 15 2.88 1.48 1.9 25 2.79 1.17 2.4 35 2.68 0.99 2.7

As can be seen from Table 1: 35 minutes after the injection ofradiopharmaceuticals, the cerebral cortex uptake ratio of the model miceto the control mice was 2.7, higher than the boron ratio (2.5) of thetarget and the non-target in the effective boron neutron capturetherapy. The results suggest that radioactive6-borono-2-(4-methylaminophenyl)benzothiazole can be effectively boundto the amyloid β-protein deposition plaque and accumulate at the lesion.It is more desirable for the patients with Alzheimer's disease treatedwith boron neutron capture therapy, the lesions can accept a largenumber of radiation dose, to achieve the purpose of treatment, andreduce the radiation damage to the normal brain tissue.

TABLE 2 The uptake of radioactive 6-borono-2-(4-methylaminophenyl)benzothiazole in hippocampus of model mice andcontrol mice hippocampus uptake of Time after radiopharmaceuticals (%ID/g) radiopharmaceutical Model Control Ratio (model injection (min)mice mice mice/control mice) 5 3.44 1.80 1.9 15 3.50 1.49 2.3 25 3.451.09 3.2 35 3.27 1.01 3.2

As can be seen from Table 2, 25 and 35 minutes after the injection ofradiopharmaceuticals, the hippocampus ratio of the model mice to thecontrol mice was 3.2, higher than the boron ratio (2.5) of the targetand the non-target in the effective boron neutron capture therapy. Theresults also suggest that radioactive6-borono-2-(4-methylaminophenyl)benzothiazole can be effectively boundto the amyloid β-protein deposition plaque and accumulate at the lesion.

SAMP8 model mice are accelerated aging mice with Alzheimer's disease,and a large number of amyloid β-protein deposition plaque areaccumulated in the cerebral cortex and hippocampus lesions. It can beseen from the experimental data of the model mice and the control micein Table 1 and Table 2 that the cerebral cortex and hippocampus of theSAMP8 model mice have a stronger ability to absorb6-borono-2-(4-methylaminophenyl)benzothiazole compared to the normalcontrol mice. It is also further explained that6-borono-2-(4-methylaminophenyl)benzothiazole is specific for amyloidβ-protein are specific, and boron neutron capture therapy can be used inthe future to treat Alzheimer's disease and provide another advancedtreatment for patients with Alzheimer's disease.

According to the results of the analysis of Table 2, 25 to 35 minutesafter the injection of radioactive6-borono-2-(4-methylaminophenyl)benzothiazole in mice, the ratio ofradiopharmaceuticals in the hippocampus of the model mice and mice was3.2. Thus, the Micro-PET image of the intermediate value of 30 minuteswas used to further compare the accumulation of the radioactivity of6-borono-2-(4-methylaminophenyl)benzothiazole in the brain.

FIG. 5 is an image of PET scan and processed by AMIDE software at 30 minafter the injection of radioactive6-borono-2-(4-methylaminophenyl)benzothiazole, wherein graph A is theimage of the control mice injected with radiopharmaceutical at 30 min,in graph A, picture (1) shows the scan image of coronal section of thecontrol mouse, picture (2) is a cross-sectional view of picture (1)along the Y-axis, picture (3) is a brain cross-sectional view of picture(1) along the Y-axis; graph B is the image of the SAMP8 model miceinjected with radiopharmaceutical at 30 min, similarly, in graph B,picture (1) shows the scan image of coronal section of the controlmouse, picture (2) is a cross-sectional view of picture (1) along theY-axis, picture (3) is a brain cross-sectional view of picture (1) alongthe Y-axis.

Wherein picture (3) of graph A and picture (3) of graph B can reflectthe brain radiopharmaceutical absorption. It can be seen from comparisonof these two images, the brain of the SAMP8 model mouse in graph B (3)has accumulated a large amount of radiopharmaceuticals relative to thebrain of the control mice in graph A (3), and it is already known thatthe model mouse brain has a large number of amyloid β-protein depositionplaques, it can be explained that6-borono-2-(4-methylaminophenyl)benzothiazole is specific for amyloidβ-protein deposition plaque, and in the future 6-borono-2-(4-methylaminophenyl)benzothiazole can be used for boron neutron capture therapy.

Example 5 Experiment for Simulation of the Neutron Capture TherapySystem to Eliminate Protein

In this example, boronic acid (H₃ ¹⁰BO₃) was used in place of6-borono-2-(4-methyl aminophenyl)benzothiazole, wherein the boronelement in boric acid (H₃ ¹⁰BO₃) was ¹⁰B, and bovine serum albumin (BSA)was used to mimic amyloid β-protein. The mixed solution of boric acidand bovine serum albumin was placed in a neutron beam captureenvironment. The effect of neutron on bovine serum albumin and theeffect of neutron on bovine serum albumin in the presence of H₃ ¹⁰BO₃were analyzed by SDS-PAGE gel electrophoresis.

Effect of Neutron on Bovine Serum Albumin

A BSA solution of concentration of 0.01% (w/w) was prepared withultrapure water, and the prepared solution was stored and operated at 4°C. A 1 mL BSA solution was placed on the centerline of the exit of thecollimator of the neutron capture therapy device, wherein the distanceof the solution from the exit of the collimator was 2 cm and a neutroncapture therapy device was arranged so that the neutron intensity at theexit of the collimator was 2.4*10¹¹/s, and the BSA solution wasirradiated in the neutron environment for 2 h; another 1 mL BSA solutionwas taken as a control solution without neutron irradiation.

The BSA solution with neutron irradiation for 2 h and the controlsolution were stained with Coomassie brilliant blue and subjected toSDS-PAGE gel electrophoresis, the colors of the protein bands in theelectrophoresis pattern of the sample solution and the control solutionwere quantified by Image J software, and the values were used torepresent the relative content of protein, wherein the content of BSA inthe control solution was defined as 1. Under the above neutronirradiation experiment, the content of BSA after the neutron irradiationfor 2 h was 0.8, and its content was reduced by about 20%. It can beseen that the radiation containing the neutron beam can affect theprotein content.

II. Effect of Neutron on Bovine Serum Albumin in the Presence of H₃¹⁰BO₃

A solution of BSA and H₃ ¹⁰BO₃ was prepared with ultrapure water,wherein in the solution, the concentration of BSA was 0.01% (w/w), andthe concentration of H₃ ¹⁰BO₃ was 0.18 M; and the prepared solution wasstored and operated at 4° C. 8 parts (numbered A, B, C, D, E, F, G, H,respectively) were taken from the solution, and 1 mL of each solutionwas irradiated with a neutron capture therapy device. 8 parts of thesolution were respectively placed on the center line of the exit of thecollimator of the neutron capture therapy device, Solution A was 2 cmfrom the exit of the collimator, Solution B was 4 cm from the exit ofthe collimator, Solution C was 6 cm from the exit of the collimator, andso on. The beam at the exit of the collimator, in addition to theneutron beam, also includes gamma rays and other radiation, mainlyneutron rays that actually destroy the protein. The example describedthe intensity of the beam with the neutron intensity in the beam,wherein, the neutron strength used in the present example was2.4*10¹¹/s, and 8 parts of the solution were irradiated for 2 h in theneutron environment; and another 1 mL of the BSA and H₃ ¹⁰BO₃ solutionwas used as a control solution without neutron irradiation.

The control solution and the 8 parts of the solution irradiated by theradiation of the neutron capture therapy device were stained withCoomassie Brilliant Blue and subjected to SDS-PAGE gel electrophoresis.FIG. 6 shows the SDS-PAGE electrophoresis pattern of the controlsolution and the 8 parts of the solution.

The first two protein bands in FIG. 6 were BSA in the control solutionand the rest were BSA after exposure to the radiation. 8 parts of thesolution were placed on the center line of the exit of the collimator.Since the solutions on the center line all contain H₃ ¹⁰BO₃ and the ¹⁰Belement has a large thermal neutron capture cross section, the neutrondose decreased significantly after the neutrons in the radiation fromthe exit of the collimator were passed through the solution containingH₃ ¹⁰BO₃. The farther away from the collimator, the less the neutronradiation dose received by the BSA.

As can be seen from FIG. 6, the colors of the protein bands of the eightneutron-irradiated solution became lighter in different degrees comparedto that of the control. And the closer to the exit of the collimator,the lighter the color of the protein bands in the solutions, indicatingthe more the protein content was reduced, and the closer to the exit ofthe collimator, the greater the neutron radiation dose received by thesolution. It is further explained that the size of the neutron doseaffects the content of BSA in the solution, and the stronger the neutrondose, the less the content of BSA in the solution after the neutronirradiation.

The colors of the BSA protein bands in the electrophoresis patternscorresponding to the control solution and 8 parts of the solution werequantified by Image J software, and the values were used to representthe relative content of the protein, wherein the content of BSA in thecontrol solution was defined as 1. Under the above neutron irradiationexperiment, the contents of BSA after neutron irradiation for 2 h areshown in Table 3.

It can be seen from Table 3, the content of BSA in the solutionirradiated by neutrons decreased to varying degrees. After 2 hours ofneutron irradiation with a neutron intensity of 2.4*10¹¹/s on thesolution placed at 2 cm from the exit of the collimator, the BSA contentthereof was only 5.3%, indicating that the neutron can greatly destroythe structure of BSA and decrease the content of BSA in the presence ofH₃ ¹⁰BO₃. And within the allowable range of experimental error, amongthe 8 solutions, the farther distance of the solution from the exit ofthe collimator, the BSA contents as a whole showed a decreasing trend,further indicating that the size of the neutron dose affected the BSAcontent.

TABLE 3 effect of neutron on bovine serum albumin in the presence of H₃¹⁰BO₃ Solution number BSA content (%) Control solution 100 A 5.3 B 2.6 C18.9 D 14.0 E 22.9 F 35.1 G 49.6 H 60.7

The compound 6-borono-2-(4-methylaminophenyl)benzothiazole provided bythe present disclosure carry a nuclide ^(m)B with a large thermalneutron capture cross section as H₃ ¹⁰BO₃ and capable of specificallybinding to the amyloid β-protein. The compound is placed in anenvironment containing amyloid β-protein, and the compound will form ahigh concentration around the amyloid β-protein. Then the region wherethe compound accumulates is irradiated with neutron beam emitted by aneutron capture therapy device, and the energy released can destroy thestructure of the protein.

While the present disclosure has been described in detail with referenceto specific embodiments thereof, it is to be noted that the aboveembodiments are provided for the purpose of further explanation of thedisclosure and are not representative of the scope of the disclosure,that non-essential modifications and adjustment made by others inaccordance with the teachings of the present disclosure is still withinthe scope of the present disclosure.

What is claimed is:
 1. A compound for specifically binding to amyloidβ-protein, wherein the compound has a structure as shown in formula I:

wherein R₁ is —B(OH)₂, R₂ is —NHCH₃; and wherein the boron element in R₁is a nuclide ¹⁰B with a large thermal neutron capture cross section. 2.The compound for specifically binding to amyloid β-protein according toclaim 1, wherein the carbon element in R₂ of the compound is ¹¹C.
 3. Aprocess for preparing the compound according to claim 1, wherein thecompound for specifically binding to amyloid β-protein is prepared fromcompounds selected from the group consisting of: formula II:

the compound of formula II is 6-bromo-2-(4-nitrophenyl)benzothiazole;formula A:

wherein R₁ is —NO₂ or —NH₂, when R₁ is —NO₂, the compound is6-borono-2-(4-nitrophenyl)benzothiazole; when R₁ is —NH₂, the compoundis 6-borono-2-(4-aminophenyl)benzothiazole; formula X:

wherein R₂ is —NO₂ or —NHCH₃, when R₂ is —NO₂, the compound is2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole;when R₂ is —NHCH₃, the compound is2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole.4. The process according to claim 3, wherein the process for preparingthe compound for specifically binding to amyloid β-protein from thecompound of formula II comprises steps of: reducing6-bromo-2-(4-nitrophenyl)benzothiazole to obtain6-bromo-2-(4-aminophenyl)benzothiazole; reacting6-bromo-2-(4-aminophenyl)benzothiazole and formaldehyde to obtain6-bromo-2-(4-methyl aminophenyl)benzothiazole; reacting6-bromo-2-(4-methyl aminophenyl)benzothiazole and bis(pinacolato)diboronto obtain 2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole;oxidizing 2-(4-methylaminophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazoleby an oxidizing agent to obtain the compound 6-borono-2-(4-methylaminophenyl)benzothiazole of formula I; wherein the boron inbis(pinacolato)diboron is ¹⁰B.
 5. The process according to claim 3,wherein the process for preparing the compound for specifically bindingto amyloid β-protein from the compound of formula II comprises steps of:reacting 6-bromo-2-(4-nitrophenyl)benzothiazole withbis(pinacolato)diboron to obtain2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole;oxidizing2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazoleby an oxidizing agent to obtain 6-borono-2-(4-nitrophenyl)benzothiazole;reducing 6-borono-2-(4-nitrophenyl)benzothiazole by a reducing agent toobtain 6-borono-2-(4-aminophenyl)benzothiazole; reacting6-borono-2-(4-aminophenyl)benzothiazole, methyl iodide and silvertrifluoromethanesulfonate to obtain the compound 6-borono-2-(methylaminophenyl)benzothiazole of formula I; wherein the boron inbis(pinacolato)diboron is ¹⁰B.
 6. The process according to claim 3,wherein the process for preparing the6-borono-2-(4-nitrophenyl)benzothiazole comprises steps of: reacting6-brom2-(4-nitrophenyl)benzothiazole with bis(pinacolato)diboron toobtain2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazole;oxidizing2-(4-nitrophenyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzothiazoleby an oxidizing agent to obtain 6-borono-2-(4-nitrophenyl)benzothiazole.7. The process according to claim 3, wherein the process for preparing6-borono-2-(4-aminophenyl)benzothiazole comprises step of: reducing6-borono-2-(4-nitrophenyl)benzothiazole to obtain6-borono-2-(4-aminophenyl)benzothiazole.
 8. The process according toclaim 5, wherein the carbon in the methyl iodide is ¹¹C.
 9. The processaccording to claim 4, wherein the oxidizing agent is sodiummetaperiodate.
 10. The process according to claim 5, wherein theoxidizing agent is sodium metaperiodate.
 11. Use of the compoundaccording to claim 1 in the preparation of a medicament for specificallybinding to amyloid β-protein.
 12. The use according to claim 11, whereinthe medicament and neutron capture therapy device are combined toeliminate amyloid β-protein.